The first map to the Jack Hall Gang treasure can be purchased from Maximo, a treasure hunter found on the ridge overlooking the river north-west of Flatneck Station and north of Bard's Crossing, for $10.00.
If you decline his initial $10 offer, he'll offer to sell you the map for $5 instead. You can also kill him and loot it from his body, or purchase it from a Fence later on.
The map depicts Caliban's Seat, a unique rock formation to the south of Valentine.
Scale the hill on the eastern side to reach the top.
Follow a path through the rocks from the top.
Move along the ledge, jumping across gaps and mantling over ledges, until you reach a large swath of white granite with a small hole in it.
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